Electrical signaling system



Feb. 28, 1950 w. sAvlLLE ETA'. 2,498,899

ELECTRICAL SIGNALING SYSTEM Filed Aug. 27, 1945 IR I I DELAY I v "TMEQHANMM Msa I INVENTORS WILLIE SAVILLE PHILIP NORTON ROSEBY ATTORNEY Patented Feb. 28., 1950 iSIGNALING 'SYSTEM Willie Saville :and `lliilip Norton "ROSeby, Liver- -fppolfEnglantL assilgnors to ,Automatic Electric .LaboratoriesY. Inc., Chicago, '.lll., a corporation vApplieatinn 27, 1915 `,Serial No. ,612,934 In Greatritain September 20, '.1944

comm (cl. 111-97) The present invention relates "to .electrical .signalling systems, and Yis more particularly vconcerned with systems of thetype in whichsignalling is effected by :the use .of highirequency currents .superimposed on electric vpower systems, the high Vfrequency current serving 'to operate a ,plurality of responding .devices connected tothe 1power distribution circuitat different points. The lexpression high Jfrequency currents" Ias used .herein 'implies that the currents concerned are .of a frequency Lwhich is high compared with the 'frequency ofthe power system, `for-instance 'audio frequency, and is not intended *to be limited :to high frequency currents as normally understood .in `the radio art.

The invention vIinds particular application to ,systems of the .type disclosed in'Briti-sh Specification No. 5253.850 ,in which the 'signals consist of current of a particular high 'frequency interrupted at a different lowfrequencyrate andthe Vresponding units, which `are all electrically tuned to the .same high-frequency, :are selectively mechanically tuned to lthe various low frequencies which distinguish the different'signals. Suitable .central station control .and signal generation imposed voltage vwill be reduced with increase or the ,power .system's load. This is undesirable Ybecamse under ,conditionsoflight'loadfthe--voltage of the superimposed .signal nnayfneach suela a .high .value as .to .cause sometransierinto adiacenft networks .and :such :leakage zmayfoe of sumcient Vmagnitude to VcauSe :false yoperation of "the signal responding devices .connected tothese networks.

According to thepresent invention-this possible difficulty is avoided by jprovidmg :arrangements for automatically regulating the "voltage .of `:the

superimposed signal vin accordance with lthe 'load conditions on the .portion o! the network to lwhich 'the respondingsdelzlces are y.con- ,nected. f

The invention "will "be 'better understood :from

the following description of onemethodiof carrying '1t into effect, reference being 'had to the accompanying Adrawing which shows the es ritial circuit `connections of .eallipment for automatically regulating Y"the :voltage orfaingh .frequency signal which `is superimposed'uponpower system.

lReferring now to the accompanying drawing, therectangle SFG represents the signal generator .which comprises `a-three-phase alternator, which is driven from a motor MI and which serves to v.superirnpose three-phase signalling currents via `leads 14 l5 and I6 upon the conductors HTI, HTZ and HT3 -of the high tension -or primary side -oi the power supply network.

'lhe vhigh frequency signals on the primary network will-extend by way of transformers, such as TR., on to the low tension lor secondary Inetworks .supplied therefrom, -the three-phase fourwire secondary network is shown having phase leads Whichare 'designated l, 2 and '3, anda neutrai lead'which is-designated N. On the secondary networks potential diferencesatsignal frequency 'will appear between the various phase leads Iand the neutral lead and hence the available signal energy for voperating the signal responding devices, not shown, which are usually connected between aphase lead and the neutral lead, will alsobe shared by the supply loads also connected .across theseleads so that the available line signal vol-tage will thus 'be reduced as the power load increases.

Between any one of the phase leads l, 2 or 3 and the `neutral lead N of the secondary network, a contact making voltmeter CV is connected by 'way of a bridge rectifier feeding circuit RB', together with a lter circuit, including capacitors Cfl and C2 and loosely coupled ironcored inductors Ll and L2, tuned to the superimposed signal frequency concerned. The high and low vvoltage contacts H and L of the volt- 1 meter CV respectively yconnect with relays RH and RL, each .of A'which has-two changeover contact ,Sets RHlv-R-H2 and RLI-RLZ, by means of 'which Ya field-regulating -rheostat 'FRR can be driven v:forwardly -or backwardly by -a reversible direct .Current motor M2 via a reduction gear l 2 soas toincrease or decrease theoutput voltage .of the signal frequency generator SFG by varying current flow-through the field-winding I3.

With the superimposed rvoltage at lthe normal lpredetermined value both the voltmeter needle 'Nandthefrheostat FRR. wi11occupythe positions shown ori-the drawing.

Asfpreviouslyrnentioned, the rectangle CU represents the control unit corresponding to the aforementioned Mackenzie patent and for simplicat'ion only the mechanical locking relay IR, the delay mechanism and Yone Aof the MORI- 'MCR4 'relays of this patent are shown. In the 'Mackenzie 'Patent 2,395,132, -when it -is 4desired to operate one ci 'the responding devices connected `operating the desired responding device.

3 to the power line, a corresponding push button is operated to cause the finder switch FA to nd the operated push button which causes the operation of the two coil mechanical locking relay IR. This relay in operating starts the startiner equipment ASE, the motor MS of the delay timing mechanism, and the signal source motor ACM for driving the signal alternators ATRI-ATRL The delay timing mechanism provides a period of time in the order of twenty seconds to allow the motor alternator set, driven by ACM, to reach its signalling speed. After the motor MS of. the

ture winding of motor M2 is as follows: positive battery at contacts B2, make contacts RLI, back contacts RH2, commutator I and armature winding of motor magnet M2, back contacts RHI, make contacts RL2 to negative battery. The above .adjusting of the generator SEG takes place duringthefpredet'ermined period` that relay B is energized, and this splash of high frequency signailing current on the secondary of the network will have no effect on the responding devices connected thereto. After the end of the Ipredetermined period ofenergization of relay B its cirdelay mechanism has run for seconds the con. tacts MS2 are closed to complete the signalling circuits to thereby transmit the proper code for Also,

shown in Fig. 4 of this patent is a eld regulator PG for regulating the current ow to the stator windings of the four alternators.

The present invention is designed to work with the Itransmitting system shown in the above mentioned Mackenzie patent. When the mechanical locking relay IR in the Mackenzie patent is operated the motor MS is started and a circuit is closed at the contacts of relay IR, and through a chain of normally closed contacts on the MCRl-MCRII relays (Fig. 4) of the Mackenzie patent to relay B. Relay B operates and closes its contacts BI to connect the high frequency vthen restores to disconnect the output of the generator SFG from the leads HTI, HT2 and HT3. The output of generator SFG is therefore connected to the power leads for a sucient time, that is, for a period of twenty seconds, to enable the output of the generator SFG to be increased or decreased as desired, dependent upon the load on the power network. It should also be mentioned that the motor M2 and reduction gear i2 also controls the eld regulator PG (Fig. 4) of the Mackenzie patent in the same manner as the gear I2 controls the arm of the rheostat connected to the eld winding I3 of generator ln this manner the field regulator PG is operated by motor M2 and gear I2 to increase or decrease the current flow to the stator windings of the alternators ATRl--ATR4 of the Mac- `kenzie patent in accordance with the load on the power network so that the proper signalling v current is transmitted. 4

If the induced high frequency voltage falls due frheostat FRR will be rotated in a counterclockwise direction and this will continue until the resultant increased output voltage of the generator SFG restores the line signal Voltage to its proper value whereupon the voltmeter needle will v restore to normal and relay RL will release. The above circuit for the energization of thearmacuit will be lopenedand it will deenergize thereby removingthe high" frequency signalling current from the `power system at contacts BI The voltage of the signal generator SFG has now been adjusted to its 'normal value in respect to the system load. The release of relay B at contacts B2 lopensthe circuit of motor M2, thereby preventing further operation of the rheostat FRR. The pulsing relays such as MCI-MC4 of the -Mackenzie patent, will now be pulsed a certain number of times at a rate corresponding to the responding device to be operated, which is connected tothe secondary network.

Similar considerations apply if the superimposed potential rises, in which case upon the seizure of the control unit CU and the first operation of relay B, the voltmeter lneedle N will connect with contact H, thereby, relay RH will be operated and at its contacts RHI and BH2 serves to drive the motor M2 and the rheostat FRR coupled thereto in the reverse direction from that mentioned above until such time' as normal line voltage conditions are restored. The path for driving the motor M2 in a clockwise direction is as follows: positive battery at `contacts B2, back contacts RLI, make contacts RHI, armature I ll of motor M2, make contacts BH2, back contacts RLZ, to negative battery.

While certain embodiments of the invention have been described, it will be obvious to those skilled in the art that changes and modications ymay be made therein and consequently the appended claims are aimed to cover all such changes Aandmcdiiications as fallwithin the true spirit and scope of the invention.

What is claimedas new and desired to .secure by Letters P atent is: l

1. In an electrical signalling system employing vhigh frequency currents superimposed on a low frequency electric power network in order to operate a plurality of responding devices connected thereto, said electric power network comprising a-gprimary network anda secondary network inductively coupled together, a control unit, a generator for .producing said high frequency currents, means .controlled by'said control unit for connesting. the output of said generator to said primary network, a contact makingv voltmeter, a ccndenseriand inductance coupling unit, tuned to said high frequency, connected to said secondary network,a rectifier .bridge connecting said voltmeter to said coupling unit, a rheostat for adjustlng the output voltageV of lsaid generator, a re- -versible motor actuating said rheostat, and means 4controlledby said voltmeter for operating said unit.

2. Inanix. electrical signalling system employing high frequency .currents superimposed on an electricsupply..nl etworkf` supplying power at a fre- 5 quency lower than said rst frequency in order to operate a plurality of responding devices connected thereto, said supply network comprising a primary network and a secondary network inductively coupled together, a control unit, a generator for producing a potential at said rst frequency, said control unit connecting the output of said generator to said primary network, a contact making voltmeter, a tuned circuit coinprising a condenser and inductance tuned to said first frequency and connected to said secondary network, a rectifier connected to said voltmeter, a coupling unit coupled to said tuned circuit for controlling the operation of said rectifier to control said Voltmeter, a rheostat for controlling the output potential of said generator actuated by a reversible motor and means controlled by the operation of said voltmeter to actuate said motor to vary the potential of said high frequency currents.

WILLIE SAVILLE. PHILIP NORTON ROSEBY.

REFERENCES CITED The following references are of record in the nle of this patent:

UNITED STATES PATENTS Number Name Date 706,575 Lunt Aug. 12, 1902 1,674,757 Bates June 26, 1928 1,710,755 West Apr. 30, 1929 1,746,756 Ashbaugh Feb. 11, 1930 1,822,439 Hahnemann et al. Sept. 8, 1931 1,943,524 Godsey, J1' Jan. 16, 1934 1,981,040 Gulliksen NOV. 20, 1934 2,046,696 Nycum July 7, 1936 2,109,215 Harder Feb. 22, 1938 2,136,248 McLachlen NOV. 8, 1938 2,141,489 Roseby Dec. 27, 1938 2,395,132 Mackenzie Feb. 19, 1946 

